True, but the do everything right probably does help quite a few people. And do everything wrong and live to a ripe old age - well there is always the possibility you could have lived even longer, or lived healthier to that old age. As you say with bowel cancer, there is still the genetic factor, as in it is thought that with some cancers there is a predisposition and to avoid the factors that trigger it seems wise. There may yet be other genetic factors to be found with all sorts of diseases. Living healthy and active into your old age is a target worth going for, not just the total in years.
By the way, on the subject of active, I'd like to recommend Stecco treatments -
Home - Manipolazione Fasciale - it can be hard work to find a practitioner, because the Stecco Institute only advertise people who have taken all four levels of qualifications. For the UK, you have to search around podiatrists, physiotherapists, chiropractors and osteopaths to find ones who've also trained in Fascial Manipulation (and avoid the Stucco websites...). What you are looking for is fascial manipulation and it will only be practiced by someone who has already trained in a hands on medical specialty that includes a thorough grounding in anatomy - as in physios etc as per earlier. There is also Fascial Relaxation which is not the same and is an alternative therapy. So having said that, what I am on about? Well, the deep fascia encloses the body and the organs and is an interwoven web of tissue. When you are injured, or even just from wear and tear, it can get bunched up into knots. That then restricts movement and makes it harder work. I've been having treatments for over a year, six points at a time (there are a lot of points) and it has made a massive difference for me in terms of bending down, walking, picking things up, twisting to the side - it is just easier, and far less tiring. I'm not at retirement age and in any case the practitioner I see was telling me about an 80+ y.o. who'd been struggling badly to walk upstairs, but after treatments to release the fascia around his hips and thighs, stairs were now easy. In the UK there are a limited number but gradually increasing. I gather there are a couple of training courses each year.
